1. Field of the Invention
This invention relates generally to couplers, and more particularly, to a coupler that can mechanically join together a plastic pipe and a concrete pipe, and still more particularly a plastic pipe that is corrugated.
2. Description of the Related Art
This invention is directed to the providing of a coupler for use with plastic and concrete pipe. Over the years, there have been many couplers for joining one plastic pipe with another pipe also made from plastic. Similarly, there have been couplers that have been made to join together two pipes fabricated from concrete. However, there has never been a coupler that can mechanically join together a concrete pipe having a smooth-walled exterior and a plastic pipe, especially one that is corrugated.
Historically, concrete and plastic pipes have not been used together in the field due to the absence of mechanical connectors. Attempts at using the screw-type of coupler used with concrete pipe on plastic pipe as well could result in the tearing of the plastic pipe if the juncture of the two pipes was subjected to stress. Additionally, many job applications only permitted the use of one type of pipe, however, recently there has been some willingness on the part of some organizations charged with overseeing transportation related pipe installations to permit concrete and plastic pipe to be used in the same job installation.
For example, one place historically where only concrete pipe has been used is in culvert applications beneath roadways. Cylindrical, smooth-walled concrete pipe typically 8′ in length is laid well beneath the road surface, extending from one side of the road to the other. Penultimate sections of concrete pipe are laid at opposing ends of the concrete pipe(s), with concrete culvert openings attached to the opposite free ends of the concrete conduit. Each of the concrete structures is coupled to the structure adjacent thereto using couplers well known in the concrete pipe industry. The installation process is time consuming and requires the use of manpower and equipment sufficient to move such heavy structures. By using HDPE (high density polyethylene) or other types of plastic pipe with similar characteristics to HDPE, the manpower and equipment requirements could possibly be lessened. Additionally, a longer plastic pipe (greater than 12′ and normally 20′ in length) could be utilized in place of several shorter concrete sections due to the weight factor. This could further reduce installation time and decrease the number of joints, thereby decreasing the number of joint leaks, as well as being cheaper due to the relative costs of the pipes involved.
It is thus apparent that the need exists for a coupler for mechanically joining concrete and plastic pipe which effectuates a watertight seal so as to be useful in culvert construction, which coupler is relatively easy to fabricate and cost effective to use.